text: Ureas describes a class of chemical compounds that share the same functional group, a carbonyl group attached to two organic amine residues: , where  groups are hydrogen (–H), organyl or other groups. Examples include carbamide peroxide, allantoin, and hydantoin. Ureas are closely related to biurets and related in structure to amides, carbamates, carbodiimides, and thiocarbamides.